Divergent Strategy in Marine Tetracyclic Meroterpenoids Synthesis

The divergent total synthesis strategy can be successfully applied to the preparation of families of natural products using a common late-stage pluripotent intermediate. This approach is a powerful tool in organic synthesis as it offers opportunities for the efficient preparation of structurally related compounds. This article reviews the synthesis of the marine natural product aureol, as well as its use as a common intermediate in the divergent synthesis of other marine natural and non-natural tetracyclic meroterpenoids.     

Simulation of soil organic carbon stocks in a Mediterranean olive grove under different soil-management systems using the RothC model

Agricultural soils play a very important role in regulating the carbon dioxide (CO₂) content of the atmosphere, and can behave either as carbon sources or sinks. We have simulated the dynamics of carbon in the soil under different land uses and soil-management systems in a Mediterranean olive grove with the Rothamsted carbon (RothC) model. To this end we chose patches of native vegetation (NV) and two different olive grove soils (chromic calcisols and calcic vertisols) under different soil-management systems: conventional tillage (T), and mulching with shredded olive-pruning debris and residues from olive-fruit cleaning (PD + CR). We measured the clay content, bulk density, soil organic carbon (SOC) and total nitrogen (N) in each patch. The SOC and N values decreased by more than 30% as a result of a change in soil use from NV to T olive grove. After adding PD + CR these values rose once more, even to levels above NV. The RothC model performed well for covered soils (NV and PD + CR) but overestimated the SOC values after the soil use was changed from NV to T olive grove, probably due to high carbon losses caused by erosion, common to T soils in the Mediterranean basin. As a result of mulching the soil with only pruning debris, CO₂ emitted to the atmosphere was reduced by >55% for both soils. Associated with this decrease in the emission rate, RothC estimated a potential carbon sequestration of 0.5 and 0.6 t C/ha/yr for chromic calcisols and calcic vertisols, respectively. The reuse of organic debris generated in the olive grove, such as pruning debris and residues from olive-fruit cleaning, is an efficient way of improving soil properties, diminishing CO₂ emissions and increasing the soil’s capacity to store carbon.     

Drought Impacts Mineral Contents in Andean Potato Cultivars

Mineral micro‐ and macronutrients in tubers of 21 Andean potato cultivars were investigated in a field trial under control and drought conditions. Mineral concentrations in potato tubers were highly variable between genotypes; some were significantly and positively correlated with each other, the most noteworthy associations being Na–Ca, Mn–Mg and Zn–Fe, in both control and drought‐stressed plants. Overall, increasing yields are related to decreased concentrations of some nutrients, albeit some higher‐yielding cultivars also displayed important concentrations of nutrients in their tubers. The most striking result was the increase in the concentration of the majority of the analysed cations in a large number of cultivars in response to water depletion; some of them, such as K, may be related to water homeostasis and/or to sucrose loading and unloading in phloem sap. Tuber mineral concentrations were not related to drought tolerance in terms of tuber productivity. Interestingly, yield loss under drought was not correlated with yield potential under control conditions. Identification of cultivars such as 703264 and 701106 able to maintain good yield stability in association with high mineral contents under water deprivation is of particular interest, especially in view of the importance of potato as a staple crop and the expansion of its cultivation to non‐optimal cultivation areas in the context of changing climatic conditions.     

Isolation, identification, and pathogenicity of two field strains of infectious bursal disease virus

Using a sentinel bird approach, two field isolates of infectious bursal disease virus (IBDV) were isolated from broiler farms in two major broiler-producing areas of the state of Georgia. These farms had a history of subclinical IBD associated with respiratory problems and poor performance. Isolates designated as U-28 and 3212 were isolated using specific-pathogen-free chicken embryos and chicken embryo bursal cells. These isolates were identified by means of agar gel precipitation and virus-neutralization tests, direct immunofluorescence, histopathology, and electron microscopy. Isolates U-28 and 3212 appear to differ in antigenicity and pathogenicity from previously known serotype I IBDV isolates. In evaluating the extent of bursal damage caused by these field isolates, an association was found between the bursa of Fabricius/body weight index, histopathology scoring of atrophy, and morphometric analysis of the total follicle area.     

Genetic heterogeneity of bovine viral diarrhoea virus (BVDV) isolates from Turkey: identification of a new subgroup in BVDV-1

Genetic heterogeneity of Turkish ruminant pestiviruses was investigated by phylogenetic analysis of complete N(pro) encoding nucleotide sequences. A total of 30 virus isolates obtained from 15 provinces around the country between 1997 and 2005 were included in the phylogenetic analysis. Virus isolates mostly originated from cattle with one isolate from sheep. The bovine isolates all belonged to BVDV-1, the sheep isolate to BVDV-2. Fifteen isolates formed a new subgroup within BVDV-1, tentatively named BVDV-1l. The remaining bovine isolates were typed as BVDV-1a (n=4), BVDV-1b (n=4), BVDV-1d (n=3), BVDV-1f (n=2) and BVDV-1h (n=1). The isolates allocated to BVDV-1l originated from various geographical regions in different years. There was no correlation between genetic grouping and locations where isolates were obtained. Viruses originating from one farm in most cases belonged to the same subgroup (n=5). This study indicates that the newly detected subgroup BVDV-1l is predominant and widespread in Turkey. Moreover, an ovine virus isolate was identified as the first member of BVDV-2 reported in Turkey. A serological survey using samples from western Turkey indicated that BVDV-2 is also present in cattle.     

Morphological characteristics and composition of lipophilic extractives and lignin in Brazilian woods from different eucalypt hybrids

The morphological and chemical characteristics of the woods from several eucalypt hybrids from the Brazilian Genolyptus program were studied. The hybrids selected for this study were Eucalyptus grandis × E. urophylla (IP), E. urophylla × E. urophylla (U1 × U2), E. grandis × [E. urophylla × E. globulus] (G1 × UGL), and [E. dunnii × E. grandis] × E. urophylla (DG × U2). The analyses of the lipophilic extractives indicated a similar composition in all eucalypt hybrids, which were dominated by sitosterol, sitosterol esters and sitosteryl 3β-d-glucopyranoside. These compounds are responsible for pitch deposition during kraft pulping of eucalypt wood. Some quantitative differences were found in the abundances of different lipid classes, the wood from U1 × U2 having the lowest amounts of these pitch-forming compounds. The chemical composition and structure of lignins were characterized by Py-GC/MS and 2D-NMR that confirmed the predominance of syringyl over guaiacyl units and only showed traces of p-hydroxyphenyl units in all the woods, with the highest S/G ratio for G1 × UGL. The 2D-NMR spectra gave additional information about the inter-unit linkages in the lignin polymer. All the lignins showed a predominance of β-O-4′ ether linkages (75-79% of total side-chains), followed by β-β′ resinol-type linkages (9-11%) and lower amounts of β-5′ phenylcoumaran-type, β-1′ spirodienone-type linkages or β-1′ open substructures. The lignin from the hybrid G1 × UGL presented also the highest proportion of β-O-4′ linkages, and therefore, it is foreseen that the wood from this hybrid will be more easily delignifiable than the other selected Brazilian eucalypt hybrids. In complement to these chemical analyses, the morphological characterization of fibers, vessels and fines revealed that hybrid eucalypt clone DG × U2 presented the most interesting properties for the manufacture of paper pulps and biofuels.     

Natural Products from Antarctic Colonial Ascidians of the Genera Aplidium and Synoicum: Variability and Defensive Role

Ascidians have developed multiple defensive strategies mostly related to physical, nutritional or chemical properties of the tunic. One of such is chemical defense based on secondary metabolites. We analyzed a series of colonial Antarctic ascidians from deep-water collections belonging to the genera Aplidium and Synoicum to evaluate the incidence of organic deterrents and their variability. The ether fractions from 15 samples including specimens of the species A. falklandicum, A. fuegiense, A. meridianum, A. millari and S. adareanum were subjected to feeding assays towards two relevant sympatric predators: the starfish Odontaster validus, and the amphipod Cheirimedon femoratus. All samples revealed repellency. Nonetheless, some colonies concentrated defensive chemicals in internal body-regions rather than in the tunic. Four ascidian-derived meroterpenoids, rossinones B and the three derivatives 2,3-epoxy-rossinone B, 3-epi-rossinone B, 5,6-epoxy-rossinone B, and the indole alkaloids meridianins A–G, along with other minoritary meridianin compounds were isolated from several samples. Some purified metabolites were tested in feeding assays exhibiting potent unpalatabilities, thus revealing their role in predation avoidance. Ascidian extracts and purified compound-fractions were further assessed in antibacterial tests against a marine Antarctic bacterium. Only the meridianins showed inhibition activity, demonstrating a multifunctional defensive role. According to their occurrence in nature and within our colonial specimens, the possible origin of both types of metabolites is discussed.     

Geochemical speciation of chromium related to sediments properties in the riverbed contaminated by tannery effluents

Journal of Soils and Sediments - Guadalentin River (SE Spain) has been affected by tannery industries, where their effluents, containing Cr, were spilled until 2003. The untreated tannery effluent...